France Says New Roofs Must Be Covered in Plants or Solar Panels

According to a new French law approved on Thursday, rooftops on new buildings in commercial zones across France must either be partially covered in plants or solar panels.

Green roofs, which cover rooftop space with a layer of grasses, shrubs, flowers, and other forms of flora, offer a number of benefits.  They create an insulating effect, reducing the amount of energy needed to heat or cool a building depending on the season. They increase local access to green space, which often comes at a premium in urban environments.  They retain rainwater, thus decreasing runoff and any related drainage issues. They provide a space for urban wildlife, such as birds, to congregate and even nest, and they reduce air pollution by acting as natural filters.

Green rooftops also significantly reduce the urban “heat island” effect in which urban areas are noticeably warmer than their surroundings.  The heat island effect can cause large cities to get 1.8°F to 5.4°F warmer than surrounding areas in the day, and 22°F warmer at night, according to the EPA.  This effect happens when buildings, roads, and other developments replace formerly open land and greenery, causing surfaces to become moist and impermeable, and to warm up.

Approved by French Parliament, the law was scaled back from initial proposals by environmental groups asking for green roofs to cover the entire rooftop surface of all new buildings.  The compromise gave businesses a choice to install solar panels instead or to only cover part of the roof in foliage.

Even in a trimmed-down form, the law is trailblazing and will both change the urban landscape of cities across France as well as potentially inspire other countries to follow suit, especially with the United Nations’ climate summit coming to Paris at the end of the year.

France has lagged behind other major European countries like Germany, Italy and Spain in solar power development.  As of last summer, France had just over five gigawatts of photovoltaic capacity, accounting for around one percent of total energy consumption. Germany has nearly 40 GWs installed.  France is heavily reliable on nuclear power for its energy, and nuclear generation in 2012 made up about 83 percent of the country’s total generation.

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